It has long been known in the disposable absorbent bandage art that it is extremely desirable to construct absorptive devises such as disposable diapers, catamenials, sanitary napkins, incontinent articles, and the like, presenting a dry surface feel to the user to improve wearing comfort and to minimize the development of undesirable skin conditions due to prolonged exposure to moisture absorbed within the bandage.
One viable prior art solution to the aforementioned problem is disclosed in commonly assigned U.S. Pat. No. 4,342,314 issued to Radel and Thompson on Aug. 3, 1982 and hereby incorporated herein by reference. Radel et al. discloses an absorbent bandage with a wearer-contacting topsheet comprising a resilient macroscopically expanded, three-dimensional, plastic web exhibiting a combination of fiber-like and plastic properties. In a preferred embodiment, the macroscopically expanded, three-dimensional, plastic web topsheet disclosed in Radel et al. exhibits a fine scale three-dimensional microstructure comprising capillary networks originating in and extending from one surface of the web and terminating in the form of apertures in the opposite surface thereof to promote rapid fluid transport. The web's fiber-like appearance is comprised of a continuum of fiber-like elements, the opposed ends of each of the fiber-like elements are interconnected to at least one other of the fiber-like elements.
A typical capillary network in the Radel et al. structure comprises an uppermost capillary opening formed by a multiplicity of primary fiber-elements interconnected to one another in the uppermost plane of the web. The uppermost opening may, if desired, be further subdivided into smaller capillary openings by secondary and tertiary fiber-like elements at planes located below the wearer-contacting surface of the web.
Each of the fiber-like elements exhibits a substantially uniform U-shaped cross-section along its length. In the case of a primary fiber-like element, its cross-section comprises a base portion located in the wearer-contacting plane and a sidewall portion joined to each edge of the base portion, the sidewall portions extend generally in the direction of the absorbent pad-contacting surface of the web. The sidewall portions which intersect one another are joined to one another intermediate the wearer contacting surface and the absorbent pad contacting surface of the web, thereby forming a capillary network interconnecting the opposed surfaces of the web. The secondary and tertiary fiber-like elements, when employed, are generally similar, but originate in planes below the wearer-contacting surface of the web.
A topsheet of the type generally disclosed by Radel et al. is highly effective in promoting rapid fluid transfer from the first wearer-contacting surface to the second absorbent pad-contacting surface of the topsheet. Accordingly, topsheets of this type have enjoyed widespread commercial success on catamenial pads due to their clean and dry appearance in use when contrasted to conventional nonwoven fibrous topsheets. While the Radel et al. topsheet is highly effective in promoting rapid transfer of bodily fluids from the first wearer-contacting surface to the second absorbent pad-contacting surface, the topsheet is secured to the absorbent core with an adhesive. Unfortunately, adhesives have a tendency to clog the apertures if applied too heavily. If the apertures become clogged, fluid is not permitted to drain through the topsheet thereby exposing the skin to moisture. In addition, bonding layers together with an adhesive to ensure fluid transporting contact throughout can produce a stiff structure which is uncomfortable. Furthermore, adhesives may not provide sufficient contact between the topsheet and the underlying layers if applied too sparingly or may be rendered useless when wetted with body exudate.
Another prior art attempt at securing a topsheet to the underlying layer is disclosed in U.S. Pat. Nos. 4,690,679 issued Sep. 1, 1989 and U.S. Pat. No. 4,806,411 issued Feb. 21, 1989 to Mattingly, III et al. Both of these patents disclose a coextruded, apertured, two-dimensional film suitable for use as topsheet on a sanitary napkin. The coextruded film comprises a first layer of a first polymeric material and a second layer of a second polymeric material. Both layers are apertured for the transmission of bodily fluids therethrough. The first polymeric material exhibits a melting point temperature which is greater than the melting point temperature exhibited by the second polymeric material. The apertured film may be thermally bonded by heating the film to a temperature in excess of the melting point temperature of the second layer material and below the melting temperature of the first layer material. While this two-dimensional apertured film may be well suited for thermal bonding it would not function well as a topsheet on an absorbent article. Since the entire nonaperatured portion of the second polymeric material will be thermally bonded to the underlying layer, e.g., the absorbent core, a relatively stiff sanitary napkin will be created due to the excessive amount of bonding between the topsheet and the absorbent core. Furthermore, the two-dimensional topsheet does not provide sufficient standoff from the absorbent core for the wearer. Accordingly, even as fluid is permitted to pass through the apertures provided in the two-dimensional topsheet, the wearer's skin is placed in intimate contact with the bodily fluids which have been absorbed by the absorbent core.
Accordingly, it is desirable to provide an absorbent article having a topsheet sheet which may be thermally bonded to the absorbent core and yet maintain the flexibility, resilience, and standoff of the prior art commercially successful three-dimensional formed-film topsheets.